On the authority of Anas ibn Malik, who said: The Messenger of Allah (peace and blessings be upon him) said: "Say: He is Allah, the One" equals one-third of the Qur'an. (1)

3789 - 'Ali ibn Muhammad narrated to us, Waki' narrated to us, from Sufyan, from Abu Qays al-Awdi, from 'Amr ibn Maymun, from Abu Mas'ud al-Ansari, who said: The Messenger of Allah (peace and blessings be upon him) said: "Allah is One, the Unique, the Eternal Refuge — it equals one-third of the Qur'an." (2)

53 - Chapter on the Virtue of Remembrance (Dhikr)

3790 - Ya'qub ibn Humayd ibn Kasib narrated to us, al-Mughirah ibn 'Abd al-Rahman narrated to us, from 'Abdullah ibn Sa'id ibn Abi Hind, from Ziyad ibn Abi Ziyad, the freed slave of Ibn 'Ayyash, from Abu Bahriyyah--------------------------------------------

(1) Its chain of transmission is authentic.
It was also recorded by al-Tabarani in "al-Awsat" (5730), Ibn 'Adi in the biography of Jarir in "al-Kamil," and al-Diya' in "al-Mukhtarah" (2465) via the route of al-Hasan ibn 'Ali al-Khallal, with this chain.
It was also recorded as part of a hadith by al-Tirmidhi (3116) via the route of Salamah ibn Wardan, from Anas ibn Malik. And Salamah is weak.

(2) An authentic hadith, and this chain is good, though there is a discrepancy in it which we have explained in detail in our commentary on hadith (17106) of "Musnad Ahmad" from Waki' with this chain. Sufyan: he is al-Thawri, and Abu Qays: he is 'Abd al-Rahman ibn Tharwan, and Abu Mas'ud: he is 'Uqbah ibn 'Amr al-Badri, may Allah be pleased with him.
It was also recorded by al-Nasa'i in "al-Kubra" (10461) via the route of Shu'bah, from Abu Qays, with it.
It is in "Sahih Ibn Hibban" (791).